Polyketides are a large group of important bioactive compounds that include many anti-microbial agents. Most bioactive polyketides of microbial origin are made by actinomycetes, which are high GC Gram-positive bacteria frequenting both terrestrial and marine environments. Genes dedicated to the synthesis of a particular Type II polyketide are invariably clustered on the actinomycete chromosome and undoubtedly share a common evolutionary origin. In order to discover novel polyketide biosynthetic pathways from the majority of uncultured microorganisms present in the environment, all of Diversa's large insert fosmid libraries will be screened for Type II polyketide synthase genes using the large insert FACS biopanning technology developed in Phase I. Diversa's fosmid library collection will cover approximately 13950 genomes. Putative polyketide pathways will be transferred to our proprietary expression host Streptomyces diversa and extracts from the resulting clones will be analyzed for anti-microbial activity. Extracts of active clones will be chemically characterized and the corresponding fosmids will be sequenced to identify pathways that encode potentially novel compounds. S. diversa clones apparently producing new anti-microbial polyketides will be used to produce sufficient quantities of the compounds for further pre-clinical analysis (e.g. range of activity, toxicity, and mechanism of action). [unreadable] [unreadable]